This invention relates in general to an electrophotographic imaging member and more specifically, to an electrophotographic imaging member having an improved combination of adhesive layers.
One common type of electrophotographic imaging member is a multilayered photoreceptor. Multilayered photoreceptors member is a comprise a substrate, an electrically conductive layer, a hole blocking layer, an adhesive layer, a charge generating layer, and a charge transport layer. In web type embodiments, an anti-curl backing layer is often utilized. Multilayered photoreceptors may comprise a charge generating layer comprising finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin binder or a homogeneous material such as a vapor deposited compound. U.S. Pat. No. 4,265,990 discloses a layered photoreceptor having separate charge generating (photogenerating) and charge transport layers. The charge generating layer is capable of photogenerating holes and injecting the photogenerated holes into the charge transport layer.
Although excellent toner images may be obtained with multilayered photoreceptors, it has been found that as more advanced, higher speed electrophotographic copiers, duplicators, and printers were developed, longer life was needed for extended photoreceptor cycling. This was particularly desirable for flexible belt type photoreceptors in compact imaging machines that employ small diameter support rollers for photoreceptor belt systems operating in a very confined space. Small diameter support rollers are also highly desirable for simple, reliable copy paper stripping systems which utilize the beam strength of the copy paper to automatically remove copy paper sheets from the surface of a photoreceptor belt after toner image transfer. Unfortunately, small diameter rollers, e.g. less than about 0.75 inch (19 mm) diameter, raise the threshold of mechanical performance criteria to such a high level that photoreceptor belt seam failure can become unacceptable for multilayered belt photoreceptors. Poor adhesion between the charge generating layer and the underlying adhesive layer can cause craking or delamination at the welded seam. In addition, collisions between the belt photoreceptor seam and cleaning blades during imaging cycling can accelerate belt failure. Moreover, cracks in the seam tend to accumulate toner particles which are eventually expelled from the seam cracks during cycling and float to and deposit on critical components of the electrophotographic imaging system such lenses and corotron wires. Thus, in advanced imaging systems utilizing multilayered belt photoreceptors, belt failure has been encountered during belt cycling over small diameter rollers and/or during repeated contact with cleaning blades.
In addition, poor adhesion between the charge generating layer and the underlying adhesive layer can require undesirably complex coating procedures for production runs of photoreceptor belts. Thus, for example where wide belts are coated and thereafter slit lengthwise after coating delamination during slitting requires that deposition of the charge generation layer be prevented in regions to be slit to prevent cracking or delamination during or after slitting.
While the above described imaging members exhibit desirable electrical characteristics, there is an urgent need to extend life under extended image cycling conditions. It is also important that any solution employed to improve cycling life does not produce any deleterious effects on the electrical properties and mechanical integrity of the original device.
Thus, there is a continuing need for an electrophotographic .maging member having improved cycling life.